The phone can be programmed to
recognize the user's distinct fingerprint.

This is a feature that Apple is eager to show off, but how will
they do that in stores where hundreds of people come in and out
to test out the same machines day after day?

The answer is a demo application Apple has designed specific to
the iPhone 5S demo units that will be found in Apple Stores and
Carrier stores,
9to5Mac reports.

Here's how it will work, according to 9to5Mac:

To test Touch ID, a customer can launch the demo app. In this
app, a customer can setup the device to recognize a single
fingerprint. When the setup process is complete, the application
will direct the user to place that fingerprint on the Touch ID
sensor on the Home button. The application will then show that
the Home button successfully read the fingerprint. Then, the app
will tell the user to place a different finger on the Home
button. The app will then show a red fingerprint outline to note
that the authentication was not successful.

This will help potential buyers understand the setup
process of Touch ID, and how it will work to accept or reject
fingerprints, even if the demo application does not support the
feature's full functionality (unlocking the phone and downloading
content from iTunes).The application will reset so each new
customer will be able to try out the fingerprint sensor feature
when they visit the Apple store.